There are numerous industrial applications in which small, predetermined amounts of adhesive substances must be carefully deposited and then quickly cured. They include, for example, the wiring and assembly of printed circuit boards, attachment of surface-mounted devices, temporary securement of components prior to soldering, etc. In many instances, the use of acrylic adhesives containing a photoinitiator, to cause curing to be initiated by actinic radiation (most commonly ultraviolet light), will produce optimal results with maximum economy, speed and facility of manufacture; such adhesives are commercially available from Dymax Corporation of Torrington, Conn.
It has been proposed to provide a system for wire tacking, and the like, in which a hand-held manifold incorporates both a syringe for dispensing an adhesive substance and also the means for irradiating the site, e.g., by way of a so-called "light guide" device. Such a system would of course include a control unit remote from the hand-held assembly, for effecting the discharge of the adhesive and also for generating the activating radiation.
To achieve the best results with photoinitiated adhesives, it will usually be important that the period of irradiation be closely controlled. Furthermore, for self-evident reasons the adhesive substance must not be exposed to the radiation at the time it is being dispensed, and the dispenser itself must be maintained as free as possible from extraneous adhesive. Turning the radiation source on and off to achieve intermittent emission is often impractical because of the warm-up and cool-down times that are necessary with typical UV lamps to achieve uniform operation and reignition; moreover, it will also be disadvantageous from the standpoint of longevity, since the life of a UV lamp or similar radiation source may be significantly depleted by on-off cycling.
Accordingly, it is broad object of the present invention to provide a novel system for dispensing a radiation-curable liquid (normally, an adhesive) substance, and a novel control unit for use therein, by which the substance may be dispensed and irradiated using the same, hand-held assembly, and by which the periods of liquid dispensation and irradiation may be controlled without subjecting the radiation source device to on-off cycling.
More specific objects of the invention are to provide such a system and control unit wherein both the means for effecting liquid discharge and also the radiation source are contained in a common housing, utilizing the same power supply and a common manual actuating switch, and to provide a remote, hand-held dispenser assembly which is convenient and facile to use.
Additional objects of the invention are to provide such a system and unit having the foregoing features and advantages, which may be used to efficiently and neatly achieve bonding of electrical components and other parts, and which minimize difficulties such as might result from fouling of the dispensing device.